I had the opossite problem with my last chest freezer, I wanted the foam type and it was fiberglass. Sometimes we just can't win it seems.
I was making a blast cabinet out of mine, the foam would have been better than the fiber glass for that. Any media that gets past a seal embeds and builds up in the glass matt where as the foam is normally a good tight seal as you are probably finding out as you try to remove some.
I think there are some good threads on the site already about making a blast cabinet like this.
Make sure you have nice large arms holes! I had 4" PVC handy and used it for mine, way to small. It works but I am cramped so later I will change to 6" pipe.
Get the armholes far enough apart also, I made mine a little to close but can fix that when I make larger holes.
You need a hole for a shop vac hose or such to suck out dust, also a hole to let in air is good on the opposite side, put a baffle over these holes so media and dust is not blown right out the inlet and media not sucked out the outlet. If you don't make an inlet hole for air you'll draw a vacum, like running with a clogged hose.
I just used and checked my new shopvac and it has some good media in it already, I was using a small cheap HF cabinet I bought to be portable, it has no baffle on the outlet so I will add one.
On my chest blaster I put a plastic bottle on the vac hose, had slots cut in the sides and bottom of the bottle for good air flow, put tubesock over the bottle as a filter. That seemed to work well to prevent sucking up media but let out the finer dust ok.
I was going to build a stand for mine, use it as a chest and top load it but I haven't done that yet, for now it's sitting on blocks and I sit in a short chair to use it for now.
If you make the freezer a top load then a hole in the bottom to let out media will be handy, put a pipe and ball valve into the hole so you can open it and let media run out into a bucket or such and prefferably with a lid so dust doesn't fly everywhere while dumping. That's what I will do with mine when done.
If upright you may have a problem with media pouring out when you open the door. Add some sheet metal to the box and seal well for a foot or so tall, that should stop most media from pouring out, but you'll still get some most likely unless you can seal the top of the shet tight agains the door somehow, felt weather stripping may work well for this, stuff like used around windows and doors.
Well it has been a wasted day for me here today. I went out and blasted my left handed monkey wrench and some other parts, set up the PC stuff, and before I could prep the parts to coat them it came a nasty storm! Just barely got everything put away before the rain hit!
It's nice to work outdoors sometimes, but not days like today
